<!DOCTYPE html>
<html>

<head>
    <title>Example</title>
    <style type="text/css">
        /* CSS计数器 */
        body {
            /* 初始化名为paracount的计数器，将它的值设置为1,或者在名称后面添加一个数字
                再添加其他的计数器在后面继续写名称 othercounter
             */
            counter-reset: paracount -1;
        }

        p::before {
            /* lower-alpha指定其他数值样式，默认数字 */
            content: counter(paracount,lower-alpha)". ";
            counter-increment: paracount 2;
        }
    </style>
</head>

<body>
    <a href="http://apress.com">Visit the Apress website</a>
    <p>I like <span>apples</span> and oranges.</p>
    <p>I also like <span>mangos</span> and cherries.</p>
    <a href="http://w3c.org">Visit the W3C website</a>
</body>

</html>